Generally, cutting edges on cutting instruments are manufactured by processing an appropriate feedstock having a thickness that diminishes from the beginning of the cutting edge to the ultimate edge so as to provide a cutting edge. Conventional cutting-edge forming processes typically involve grinding operations that remove material in a gradient beginning at a distance from the ultimate edge to the ultimate edge itself. The process of grinding generally involves contacting the feedstock with hard abrasive particles imbedded in a grinding wheel rotating about an axis, thereby mechanically abrading material from the feedstock. This grinding operation often is carried out with large abrasive particles that tend to leave large gouges in the surface of the cutting edge. Subsequent processes of honing and stropping are then used to reduce the depth of gouges on the cutting edge surface. Honing and stropping are both mechanical processes that remove the softer material of the cutting edge by abrasion by the harder material of the abrasive.
A cutting edge may be characterized in several ways. First, the thickness of the cutting edge at the ultimate edge determines in part the “sharpness” of the cutting edge. A thinner cutting edge will generally encounter less resistance in parting of the material being cut. Another parameter impacting the performance of a cutting instrument is the smoothness and the contour of the cutting edge and of the sides of the cutting edge extending back towards the feedstock comprising the body of the cutting instrument. An irregular contour will lead to small, even microscopic, points that penetrate the material being cut before other parts of the cutting edge encounter the substrate. This leads to some degree of tearing rather than slicing. A cutting edge having a rough surface on the sides of the cutting edge will abrade, or tear, material that passes over the sides of the cutting edge, as the material must be pushed aside to allow for passage of the cutting edge through the material being cut.
In the surgical arts, where the material being cut is living tissue, a sharp and smooth cutting edge in, for example, surgical scalpels, is of paramount interest. The making of an incision in living tissue results in trauma to that tissue, due to the work that must be imparted to the tissue in making the incision. The work required to pass a scalpel through tissue results from many factors, including edge sharpness, force applied to the blade, drag force acting on the sides of the blade, and the like. The trauma caused to tissue from an incision results in increased time required for healing, increased chance for infection, a limitation to the size of physiological structures that can be incised accurately, and unsightly scarring.
In this regard, many efforts have been made to improve the performance of cutting instruments, particularly of surgical instruments such as scalpels. For example, resort has been made to cutting instruments fabricated from diamonds, rubies, and sapphires, which are very hard materials and can be fabricated with edges that are very thin. However, these materials are very expensive and difficult to fabricate. Their hardness is actually a disadvantage in medical operations, as they tend to fracture upon encountering hard structures such as bone, thus potentially leaving fragments in the operative subject. Metals are economically processed into surgical scalpels and the like. However, difficulties with achieving sharp and smooth edges have led to efforts such as coating of cutting edges with friction-reducing materials to reduce trauma resulting from incisions.
The heightened requirements for cutting properties of surgical instruments due to the widespread introduction into clinical practice of new procedures for performing operations on vital organs and the development of microsurgical techniques have led to demands for improved methods of producing cutting instruments and improved cutting instruments themselves.
The invention provides such a method for producing improved cutting instruments and provides improved cutting instruments themselves. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.